This invention relates to improved apparatus and methods for facilitating the connection of added pipe sections into a drill string which contains an instrument connected by a flexible conductive line to a readout unit or other unit at the surface of the earth. Though it will be apparent that the invention is applicable broadly to the drilling of a well or hole in any direction into the earth, that is, either vertically, horizontally (as in coal mining operations), or at any selected inclination, the invention will be described primarily as applied to the drilling of a vertical well.
During many drilling operations, it is helpful to provide within the drill string an instrument which can sense or respond to condition or conditions in the well, or which can serve some other useful purpose relating to the drilling process. One such instrument often employed in a drill string is a device capable of sensing the inclination of the string and the azimuth of that inclination at any particular instant, to provide information indicating to a driller what steps are necessary or desirable in order to assure that continued drilling occurs along a desired path and will ultimately reach a particular target area in the earth formation. An instrument capable of monitoring inclination and the azimuth of the inclination during drilling is shown in U.S. Pat. No. 3,791,043, and includes an instrument probe to be contained in the drill string and connected by a flexible conductive line to a readout unit at the surface of the earth on which the inclination and azimuth are indicated. An improved probe for this purpose is shown in U.S. Pat. No. 3,862,499.
U.S. Pat. Nos. 4,143,721 and 4,153,120 disclose methods and apparatus for use in conjunction with inclination instruments of the above-discussed types, or other instruments which are connected to surface equipment by a flexible conductive line, and which apparatus and methods are especially designed to enable the instrument and its flexible line to remain in the drill string while a pipe section is being added to the outer end of the string to increase its length. If the instrument and line can be left in the string during such addition of a section to its outer end, a great deal of time and effort can be saved as compared with the time and effort expanded under the more conventional procedure of completely withdrawing the instrument and line from the drill string each time that a section is added.
Other arrangements having a flexible line which is left in a drill string while a pipe section is added to the string are shown in U.S. Pat. Nos. 3,825,078; 3,825,079; and 3,913,688. In those patents, the line is passed about guides in a sheave or pulley system in a manner causing a weighted loop of the line to be shortened when the upper end of the line is pulled upwardly. The patents mention in a very general way that the line may be arranged in the drill string in a wound, helical, coiled, looped, folded, overlapped or other convoluted configuration, but contain no teaching as to any such configuration other than the above discussed pulley system.